U.S. patent application number 11/544264 was filed with the patent office on 2008-04-10 for method and system for removing ash from a filter.
Invention is credited to Pronob Bardhan, Weiguo Miao, Joseph James St. Angelo, Benjamin Allen Stevens.
Application Number | 20080083334 11/544264 |
Document ID | / |
Family ID | 38888303 |
Filed Date | 2008-04-10 |
United States Patent
Application |
20080083334 |
Kind Code |
A1 |
Bardhan; Pronob ; et
al. |
April 10, 2008 |
Method and system for removing ash from a filter
Abstract
This invention is directed to a method and system for removing
ash, particularly a heat-treated ash deposit from a filter. At
least a majority (e.g., greater than 50 wt %) of the ash is removed
as a result of the process. The filter containing the ash deposit
is contacted with an acid composition to remove a majority of the
ash, and the acid-contacted filter is then treated to remove at
least a portion of the acid.
Inventors: |
Bardhan; Pronob; (Corning,
NY) ; Miao; Weiguo; (Corning, NY) ; St.
Angelo; Joseph James; (Campbell, NY) ; Stevens;
Benjamin Allen; (Painted Post, NY) |
Correspondence
Address: |
CORNING INCORPORATED
SP-TI-3-1
CORNING
NY
14831
US
|
Family ID: |
38888303 |
Appl. No.: |
11/544264 |
Filed: |
October 6, 2006 |
Current U.S.
Class: |
95/281 ;
96/233 |
Current CPC
Class: |
F01N 3/023 20130101;
F01N 3/0237 20130101; B01D 41/04 20130101 |
Class at
Publication: |
95/281 ;
96/233 |
International
Class: |
B01D 46/04 20060101
B01D046/04 |
Claims
1. A method for removing ash from a filter, comprising: providing a
particulate filter having ash deposited thereon; contacting the
filter containing the ash deposit with an acid composition to
remove at least a portion of the ash from the filter; and treating
the acid-contacted filter to remove at least a portion of the acid
from the filter.
2. The method of claim 1, wherein the acid composition has a pH of
less than or equal to 3.
3. The method of claim 1, wherein the acid-contacted filter is
treated by rinsing with a solution to remove at least a portion of
the acid and thereby neutralize the filter.
4. The method of claim 1, wherein the ash deposited on the filter
is a heat-treated deposit that has been heated at a temperature of
at least 700.degree. C.
5. The method of claim 1, wherein the acid composition includes at
least one organic or inorganic acid.
6. The method of claim 1, wherein the acid composition contacts the
ash deposited filter at a total volume of acid composition to
filter of from 0.1:1 to 3:1.
7. The method of claim 1, wherein the acid composition contacts the
ash deposited filter for not more than one hour.
8. The method of claim 1, wherein the filter is a ceramic filter
comprised of at least one component selected from the group
consisting of cordierite, mullite, alumina, zirconium phosphate,
silicon carbide, silicon nitride and aluminum titanate.
9. A method for removing ash from a ceramic filter, comprising:
providing a ceramic filter having ash deposited thereon; contacting
the filter containing the ash deposit with an acid composition to
remove at least a portion of the ash from the filter, wherein the
acid composition has a pH of less than or equal to 3; and water
rinsing the acid contacted filter to remove at least a portion of
the acid from the acid contacted filter.
10. The method of claim 9, wherein the ash deposited on the filter
is a heat-treated deposit that has been heated at a temperature of
at least 700.degree. C.
11. The method of claim 9, wherein the ceramic filter is comprised
of at least one component selected from the group consisting of
cordierite, mullite, alumina, zirconium phosphate, silicon carbide,
silicon nitride and aluminum titanate.
12. The method of claim 9, wherein the water rinsed filter is dried
following rinsing.
13. The method of claim 9, wherein the ash deposited filter is
contacted with vapor to remove at least a portion of ash contained
on the ash deposited filter prior to contacting with the acid
composition.
14. The method of claim 9, wherein the acid composition includes at
least one organic or inorganic acid.
15. The method of claim 9, wherein the acid composition contacts
the ash deposited filter at a total volume of acid composition to
filter of from 0.1:1 to 3:1.
16. The method of claim 9, wherein the acid composition contacts
the ash deposited filter for not more than one hour.
17. The method of claim 9, wherein the filter containing the ash
deposit is provided from an exhaust housing of a diesel engine
system.
18. The method of claim 17, wherein the filter containing the ash
deposit is provided from an exhaust housing of a diesel engine
system after 100,000 miles of operation.
19. A system for removing ash from a filter, comprising: an acid
container for containing an acid composition; a pump and injection
line connected to the acid container; a housing to hold the filter;
a nozzle extending from the injection line and into the housing,
and apertured to spray the acid composition over the filter
contained in the housing; and a collection line for removing the
acid solution from the housing.
20. The method of claim 19, wherein the nozzle includes a rotating
head.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a method and system for removing
ash from a filter. In particular, this invention relates to a
method and system for removing a heat-treated ash deposit from an
exhaust filter.
[0003] 2. Technical Background
[0004] Particulate filters are used to remove particulates such as
soot and ash from exhaust systems, particularly engine exhaust
systems. In general, soot that collects on the filter can be
removed from the filter through regeneration, which is essentially
carried out by heating or burning the soot that has been collected
in the filter. Ash, however, is a non-combustible particulate
material, and cannot be removed from the filter simply by
regeneration. As ash deposit builds, the filter becomes less
effective due to a resulting increase in back-pressure.
[0005] U.S. Patent Publication No. 2006/0070360 discloses a system
for removing particulate deposits from a filtering device. The
disclosed system includes a gas pressurization assembly that is
removably connectable to the filtering device and includes a
plurality of orifices. The orifices are positioned on the filter
surface so as to direct a flow beyond at least one blocking
apparatus of the filtering device. The system also includes a
matter collection assembly removably connectable to the filtering
device.
[0006] U.S. Pat. No. 7,025,811 is directed to a cleaning device for
cleaning diesel particulate filters. The device comprises a source
of high pressure fluid and means to transport the fluid to a nozzle
or nozzles; an actuator for moving the nozzles; a controller with
logic for instructing the actuator to automatically move the nozzle
or nozzles across the surface of the filter; a collection device
and suction device downstream of the filter; and ducting to
transport the fluid between parts of the system. A second
collection device is used downstream of the suction device to
provide additional particulate removal. The system cleans
particulate material from the filter by rotating the filter and
rotating a jet about an axis outside of the filter; moving a nozzle
in two perpendicular directions (i.e., x-y); and rotating a
rectangular nozzle about the central axis of the filter.
[0007] U.S. Pat. No. 7,047,731 discloses a method for reducing
diesel contaminant and additive particulate matter in an internal
combustion engine particulate filter. The method involves
entraining contaminant and additive particulate matter in an
active, pulsating positive pressure fluid stream flowing in a
direction opposite a fluid flow direction through an installed
particulate filter during normal operation. The fluid stream is
flowed while applying a negative pressure to the installed
filter.
[0008] U.S. Patent Publication No. 2005/0011357 discloses a system
for flushing ash from a diesel particulate filter. The system
includes a conduit for supplying a fluid from a fluid supply to an
outlet of a diesel particulate filter. A pump slowly reverse flows
the fluid through the diesel particulate filter, and an acoustic
wave source generates an acoustic wave, such as an ultrasonic wave,
through the fluid in the diesel particulate filter to assist in
dislodging the ash from the diesel particulate filter, while the
fluid carries the ash out the inlet of the diesel particulate
filter. The ash may be filtered from the fluid after the fluid
exits the diesel particulate filter, so that the fluid may be
reused.
[0009] The particular systems for removing ash particulate matter
are not fully effective in removing ash deposit, particularly a
heat-treated ash deposit. It would therefore, be beneficial to
reduce or eliminate the ash deposit so that such filters can be
more effectively used.
SUMMARY OF THE INVENTION
[0010] This invention provides a method and system for removing ash
deposits from filters. The method and system are particularly
effective in removing heat-treated ash deposit from particulate
filters.
[0011] According to this invention, an ash deposit on a filter, for
example a particulate filter, can be removed using an acid wash. In
one embodiment of the invention, there is provided a method for
removing ash from a filter that includes the steps of providing a
particulate filter having ash deposited thereon; and contacting the
filter containing the ash deposit with an acid composition to
remove at least a portion of the ash from the filter. The
acid-contacted filter is preferably treated, more preferably by
water treating, to remove at least a portion of the acid from the
filter.
[0012] In one embodiment, the acid composition has a pH of less
than or equal to 3. Preferably, the acid-contacted filter is
treated by rinsing with a solution to remove at least a portion of
the acid and thereby neutralize the filter.
[0013] In another embodiment, the ash deposited on the filter is a
heat-treated deposit. In a particular embodiment, the ash deposited
on the filter is a heat-treated deposit that has been heated at a
temperature of at least 700.degree. C.
[0014] In one embodiment of the invention, the acid composition
includes at least one organic or inorganic acid. Preferably, the
acid composition contacts the ash deposited filter at a total
volume of acid composition to filter of from 0.1:1 to 3:1. It is
also preferred that the acid composition contacts the ash deposited
filter for not more than one hour.
[0015] In another embodiment, the filter is a ceramic filter.
Preferably, the ceramic filter is comprised of at least one
component selected from the group consisting of cordierite,
mullite, alumina, zirconium phosphate, silicon carbide, silicon
nitride and aluminum titanate.
[0016] In yet another embodiment, the treated or water rinsed
filter is dried following rinsing. Optionally, the ash deposited
filter is contacted with vapor to remove at least a portion of ash
contained on the ash deposited filter prior to contacting with the
acid composition.
[0017] In a particular embodiment, the filter containing the ash
deposit is provided from an exhaust housing of a diesel engine
system. The filter containing the ash deposit is preferably
provided from an exhaust housing of a diesel engine system after
100,000 miles of operation.
[0018] According to another aspect of the invention, there is
provided a system for removing ash from a filter. Preferably, the
system includes an acid container for containing an acid
composition; a pump and injection line connected to the acid
container; a housing to hold the filter; a nozzle extending from
the injection line and into the housing, and apertured to spray the
acid composition over the filter contained in the housing; and a
collection line for removing the acid solution from the housing. In
one embodiment, the nozzle includes a rotating head.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Examples of various embodiments of this invention are shown
in the attached Figures, wherein:
[0020] FIG. 1 is one example of a system that can be used to remove
ash from a filter;
[0021] FIG. 2 is a sectional view of the housing used in FIG.
1;
[0022] FIG. 3 is one embodiment of a housing that is connected to
an air compressor and a vacuum unit;
[0023] FIG. 4 is a graph showing the results of an example in which
ash-coated filters were baked at different temperatures and cleaned
with air and water to determine the effectiveness of the air
cleaning methodology on filter performance; and
[0024] FIG. 5 is a graph showing the effectiveness of cleaning an
ash coated filter using a nitric acid solution compared against
distilled water.
DETAILED DESCRIPTION OF THE INVENTION
[0025] This invention is directed to a method and system for
removing ash and/or soot from a filter. The method and system are
particularly beneficial in that they enable non-combustible
particulate deposits such as ash to be effectively removed from a
filter provided with or containing such ash. At least a portion,
preferably a majority (e.g., greater than 50 wt %) of the ash is
removed as a result of the process. More preferably, at least 75 wt
% is removed, still more preferably at least 90 wt %, and most
preferably at least 98 wt % of the ash is removed.
[0026] In general, the filter containing the ash deposit is
contacted with an acid-containing composition to remove a majority
of the ash. The acid-contacted filter is then treated to remove at
least a portion of the acid.
[0027] The method of this invention can be used to remove ash
and/or soot from any filter, filtering device, or other matter
collection device capable of withstanding acid treatment. For
example, the method can be practiced on filters from diesel,
gasoline, natural gas, or other combustion engines or furnaces.
Additional examples of the types of filters that can be used
according to the method of this invention include filters from coal
power plants and/or other types of power plants. Thus, the method
of this invention can be used in conjunction with filters that can
be found on any work machine, on-road vehicle, off-road vehicle,
stationary machine, and/or other exhaust-producing machines.
[0028] The system of this invention can be used to remove ash
and/or soot from filters while the filter or filters are on the
machine or for separate cleaning of the filter when removed from
the machine. In one embodiment, the filter is removed from the
machine and treated to remove the soot and/or ash.
[0029] The filter that is to be treated according to this invention
is provided with at least a deposit of ash. Ash is considered to be
the deposit that remains after complete combustion of a fuel. This
material is, therefore, considered incombustible.
[0030] Besides the carbon mixed with the ash, there are other
non-carbon elements that are present. These non-carbon elements are
present in the ash since the fuel source typically contains other
elements besides carbon and hydrogen. The non-carbon elements can
add to the problematic nature of having an ash deposit build on a
filter. For example, fuel from combustion engines or furnaces will
often contain sulfur, nitrogen, phosphorous, and other elements
that are naturally present in the fuel. Combustion engine fuel such
as gasoline and diesel fuel will typically contain additives to aid
in combustion, reduce engine wear, engine stress, etc., during the
combustion process. In addition, lubricating oil will also leak
into the engine during combustion and this lubricating oil will
contain additional additives.
[0031] Elements that can be included in the ash deposit comprise at
least one of K, Na, Al, Ca, Cr, Cu, Fe, Mg, Mn, Mo, Ni, P, Si, Zn,
and Zr. Particularly problematic elements in the ash deposit
include at least one of Na, Al, Ca, Fe, Mg, P, Si, and Zn. Even
more problematic elements in the ash deposit include at least one
of Ca, Fe, P, and Zn.
[0032] In typical operation, filters, especially particulate
filters, are used at the exhaust end of an engine or furnace to
capture soot and/or ash particles that emerge from the exhaust.
Soot is considered to be carbon particles or dust caused by
incomplete combustion. Therefore, at least a portion of the
material contained in the ash can be combustible. On a relative
basis, soot deposit is easier to remove from a filter than ash.
[0033] When a filter containing soot becomes sufficiently hot, at
least a portion of the soot particulate will combust. At relatively
high combustion temperatures, ash deposits in the filter will
agglomerate into a hard substance. This hard substance is very
difficult if not impossible to remove using air or water as
cleaning agents. However, this substance can be effectively removed
by the process or system of this invention.
[0034] The method and system of this invention are particularly
effective in removing a heat-treated ash deposit that has been
heated at a temperature of at least 700.degree. C. A heat-treated
ash deposit that has been heated at a temperature of at least
800.degree. C. or at least 900.degree. C. can also be effectively
removed.
[0035] In one embodiment of the invention, the filter containing
the ash deposit is provided from an exhaust housing of a gasoline
or diesel engine system. Preferably, the ash deposit is provided
from an exhaust housing of a diesel engine system.
[0036] The more extensive the use, the greater the build-up of ash
deposit on the filter. Preferably, the filter is removed from the
exhaust housing after a predetermined interval of operation and
treated according to the method or system of this invention. The
predetermined interval can be based on pressure drop across the
filter or some other calculable interval. For example, the filter
in the exhaust housing of a moving machine can be provided for
treating after some interval of movement. In one embodiment, the
filter containing the ash deposit is provided from an exhaust
housing of an engine system, preferably a diesel engine system,
after 100,000 miles of operation. More preferably, the filter
containing the ash deposit is provided from an exhaust housing of
an engine system, preferably a diesel engine system, after 200,000
miles of operation, and most preferably, after 400,000 miles of
operation.
[0037] The filter that is to be used in conjunction with the method
of this invention or cleaned or treated with the system of this
invention is preferably a particulate filter. The filter that is to
be treated or cleaned has deposited thereon ash and, optionally,
soot.
[0038] In one embodiment; the filter that is provided for treatment
according to this invention is a ceramic filter. Preferably, the
ceramic filter is comprised of at least one component, particularly
a substrate component, selected from the group consisting of
cordierite, mullite, alumina, zirconium phosphate, silicon carbide,
silicon nitride and aluminum titanate.
[0039] In another embodiment of the invention, the filter that is
provided to be treated according to this invention is a particulate
filter that includes a monolith substrate. The monolithic substrate
can have any shape or geometry suitable for a particular
application and can be made of any one or more of the above noted
materials. In one embodiment, the monolith substrate is a
multicellular structure such as a honeycomb structure. Honeycombs
are multicellular bodies having an inlet and outlet end or face,
and a multiplicity of cells extending from the inlet end to the
outlet end. The walls of the cells are porous. Generally honeycomb
cell densities range from about 10 cells/in.sup.2 (1.5
cells/cm.sup.2) to about 600 cells/in.sup.2 (93
cells/cm.sup.2).
[0040] The monolithic substrate preferably has surfaces with pores
which extend into the substrate. In one embodiment, at least a
portion of the cells of the substrate at the inlet end or face is
plugged. The plugging is preferably only at the ends of the cells.
More preferably, the plugging is to a depth of about 7 to 13 mm. A
portion of the cells on the outlet end but not corresponding to
those on the inlet end are also preferably plugged. In such an
embodiment, each cell is plugged only at one end. In one
arrangement, every other cell on a given face is plugged as in a
checkered pattern. This plugging configuration allows for more
intimate contact between the exhaust stream and the porous wall of
the substrate.
[0041] In a plugged type honeycomb filter, an exhaust stream flows
into the substrate through the open cells at the inlet end, then
through the porous cell walls, and out of the structure through the
open cells at the outlet end. Filters of this type are typically
referred to as a "wall flow" filters, since the flow paths
resulting from alternate channel plugging require the fluid being
treated to flow through the porous ceramic cell walls prior to
exiting the filter. Cross flow structures can also be used.
[0042] The filters that are provided to be used in the method of
this invention can also include a coating. In one embodiment, the
coating is formed by "washcoating" a slurry of discrete-particles
of the coating material onto the substrate. Other suitable methods
include sol-gel coating, spray coating, and plasma coating.
[0043] Washcoating techniques involve forming a washcoating slurry
of the coating material particles with various binder, e.g.,
alumina, zirconia, or silica, and then contacting the slurry with
the monolith substrate. The washcoating slurry preferably has a
viscosity of about 50-2000 cp. The average particle size of the
coating material in the slurry is preferably about 0.5-40
micrometers, and more preferably about 0.5-5 micrometers. The
contacting can be done any number of times to achieve the desired
loading.
[0044] The resulting washcoated substrate is heat-treated to
improve bonding between the substrate and the coating material.
This is done by drying and calcining. The drying is done preferably
under rotating conditions. The drying temperature is preferably
about 25-200.degree. C., and more preferably at about 50.degree. C.
for at least about 1 hour. Calcination is achieved at a temperature
of 600-1100.degree. C. with a hold at that temperature for up to 4
hours. The amount of washcoat on the substrate is preferably about
20 to 60 wt. % based on the total weight of the substrate and
coating.
[0045] According to the method of this invention, a filter,
particularly a particulate filter, is provided having ash deposited
thereon. The filter is then treated by contacting with an acid
composition to remove at least a portion, preferably a majority, of
the ash from the filter. Preferably, the acid composition that is
used to contact the filter has a pH of less than or equal to 3.
More preferably, the acid composition has a pH of less than or
equal to 2, and most preferably less than or equal to 1.
[0046] The acid composition includes at least one organic or
inorganic acid. Examples of organic acids include at least one acid
of the formula:
##STR00001##
[0047] wherein R.sub.1, R.sub.2 and R.sub.3 are, independently, H,
alkyl or X, with X=F, Cl or Br. Preferably, at least one of
R.sub.1, R.sub.2 and R.sub.3 is X. Examples of other useful organic
acids include benzenesulfonic acid and derivatives of
benzenesulfonic acid.
[0048] Examples of inorganic acids useful in this invention
include, but are not limited to, HNO.sub.3, HCl, HF, HBr, H.sub.2S,
H.sub.2SO.sub.4, H.sub.3PO.sub.4, and mixtures thereof. In one
embodiment, HNO.sub.3 is included as an acid component.
[0049] The filter containing the ash deposit is contacted with the
acid composition to remove at least a portion of the ash. The
contact of the filter with the acid composition should not be for
an extensive period in order to avoid acid damage to the filter.
Preferably, the acid composition contacts the ash deposited filter
for not more than one hour. More preferably, the acid composition
contacts the ash deposited filter for not more than 30 minutes,
still more preferably not more than 10 minutes, even more
preferably not more than 5 minutes. Contacting the ash deposited
filter with the acid composition for at least 30 seconds is
preferred, more preferably for at least one minute.
[0050] The filter can be treated for ash removal in any manner
practical. In one embodiment, the filter is removed from a housing
in the exhaust system and the acid composition is sprayed or
dropped or flowed over the filter. In another embodiment, the
filter is immersed into the acid composition.
[0051] The amount of acid composition used to treat the filter need
not be extensive. As understood in this invention, the acid
composition comprises any acid compound and any diluent. The pH of
the composition is the determining factor on the amount of the acid
and diluent used. Therefore, the amount of acid composition
includes the acid and any diluent that would be used to obtain the
desired pH. In one embodiment, the acid composition contacts the
ash deposited filter at a total volume of acid composition to
filter volume of from 0.05:1 to 10:1, preferably from 0.075 to 5:1,
more preferably 0.1:1 to 3:1, and most preferably 0.5:1 to 2:1. In
cases of spraying or dropping or flowing the acid composition
across or over the filter, the total volume of acid composition
that is used can be substantially reduced by recycling the acid
composition. For example, the acid composition can contact the ash
deposited filter and the composition recycled to further contact
the filter such that the acid composition contacts the ash
deposited filter at the desired total volume of acid composition to
filter volume.
[0052] Following contact with acid composition, it is preferable to
treat the acid-contacted filter to remove at least a portion of the
acid. Preferably, the treatment will also remove at least a portion
of the ash along with the acid. In one embodiment, this treatment
includes rinsing the acid-contacted filter. The rinse material used
can be any material that neutralizes the acid component. For
example any base can be used, as well as water. In one embodiment,
the acid contacted filter is water rinsed to remove at least a
portion of the acid from the acid contacted filter.
[0053] In one embodiment of the invention, the filter that has been
treated to remove at least a portion of the acid is dried. Drying
can be beneficial in that the cleaned and dried filter can be
readily inserted back into the filter housing for immediate and
more efficient use. In a particular embodiment, the acid treated
filter is water rinsed, and the water rinsed filter is dried
following rinsing.
[0054] The filter can be dried by any practical means. Examples of
drying include flowing hot air through the filter, and placing the
filter into a dryer.
[0055] A variety of optional steps can be included in the method of
the invention. In one embodiment, the filter is regenerated prior
to acid treatment. During regeneration, a heater or some other heat
source is used to increase the temperature of the filter
components. The heater increases the temperature of trapped
particulate matter above its combustion temperature, thereby
burning away the collected particulate matter and regenerating the
filter while leaving behind additional ash. Although regeneration
may reduce the buildup of soot in the filter, repeated regeneration
of the filter typically results in a buildup of ash in the
components of the filter over time and a corresponding
deterioration in filter performance. Unlike soot, ash cannot be
burned away through regeneration. Thus, the acid treatment
preferably follows regeneration.
[0056] In another embodiment, soot or other material is blown off
the filter prior to acid treatment. In particular, the ash
deposited filter can be contacted with vapor to remove at least a
portion of soot contained on the ash deposited filter prior to
contacting with the acid composition. In one embodiment, the ash
deposited filter that is provided is contacted with air at a flow
rate of at least 300 ft.sup.3/min, preferably at least 600
ft.sup.3/min. The air is preferably supplied from an air source in
which the air is contained at a pressure of at least 25 psi,
preferably at least 50 psi, and more preferably at least 100
psi.
[0057] One example of a system that can be used to remove ash from
a filter is shown in FIG. 1. As shown in FIG. 1, a housing 100 is
used to contain a filter 102. The particular embodiment shown in
FIG. 1 includes a pump 104a and a reservoir or container 106a for
holding the acid composition, as well as a pump 104b and a
reservoir or container 106b for holding a treating solution to
neutralize the acid composition, preferably water.
[0058] In operation, the acid composition is pumped through line
108a and into header 110. From the header 110, the acid composition
is sent through a tube 112 that extends at an angle over the filter
102 and through a nozzle 114. The acid composition passes through
the open channels of the filter 102 and in a downward direction
through the filter 102. The acid composition passes around the
plugged portions 116 of the filter 102 and out through the outlet
118 of the housing 100 and on through a collection line or tube
(not shown).
[0059] Following application of the acid composition, neutralizing
fluid, i.e., water, is pumped through the line 108b and into the
header 110. From the header 110, the water is sent through the tube
112 and through the nozzle 114, which acts like a rotating head. In
this embodiment, the nozzle 114 is shown substantially parallel to
the end of the filter and is located a relatively short distance
from the surface of the filter. The water, like the acid
composition, passes through the open channels of the filter 102 and
in a downward direction through the filter 102. The water further
passes around the plugged portions 116 of the filter 112 and out
through the outlet 118 of the housing 100 and on through the
collection line.
[0060] The housing 100 also contains an inflatable seal 120. The
inflatable seal 120 is an O-ring type seal and is inflated after
the filter is loaded into the housing 100 and the housing
closed.
[0061] FIG. 2 shows a section view of the housing 200 and filter
202. A mat 204 is located between the filter 202 and the housing
200. The mat 204 prevents the filter 202 from contacting the
housing 200, as well as provides mechanical support and thermal
insulation.
[0062] FIG. 3 shows an embodiment in which an air compressor 302
and a vacuum unit 304 are connected to housing 300. This optional
embodiment can be used to remove some of the ash and more easily
removable particles from the filter prior to acid treatment.
[0063] In operation, air is blown through the housing 300 at
sufficient velocity and force to dislodge particles 306. The
particles 306 are then collected in vacuum 304. Following air
treatment, the housing 300 can be attached to a pump and reservoir
type arrangement to apply the acid composition and neutralization
fluid. For example, the housing can be attached to the embodiment
of FIG. 1 or separate pumps and reservoirs can be attached if
desired.
EXAMPLE 1
[0064] Ash was obtained from Detroit Diesel Company, which had the
composition shown in Table 1.
TABLE-US-00001 TABLE 1 Element Source of Element Wt % K K.sub.2O
0.18 Na Na.sub.2O 1.10 Al Al.sub.2O.sub.3 2.16 Ca CaO 25.0 Cr
Cr.sub.2O.sub.3 0.35 Cu CuO 0.20 Fe Fe.sub.2O.sub.3 4.61 Mg MgO
2.22 Mn MnO.sub.2 0.10 Mo MoO.sub.3 0.05 Ni NiO 0.15 P
P.sub.2O.sub.5 23.5 Si SiO.sub.2 2.89 Zn ZnO 12.2 Zr ZrO.sub.2
0.19
[0065] Filters that were tested were Corning Dura Trap.RTM. CO
filters. Each filter was manually loaded with the ash composition,
and then placed in an oven at varying temperatures to "bake" the
ash onto the filter, similar to conditions that would occur in
actual operation. After 1 hour, the filters were removed from the
oven and air-cleaned at 100 psi pressure. The results of baking 10
different ash-coated filters at different temperatures are
indicated in FIG. 4. The results indicate that the higher the
temperature at which the filters are baked, the greater the ash
retention and thus the less effective air-cleaning is.
EXAMPLE 2
[0066] A screening experiment was performed in which a sample of
the ash was placed in a beaker and solutions of varying pH
(including de-ionized (DI) water) were poured over the ash and into
the beaker. Over various periods of time, the beakers were visually
observed for color changes to the initially clear solution. The
results of varying pH and times are shown in Table 2.
TABLE-US-00002 TABLE 2 Time pH = 1 pH = 2 pH = 3 pH = 4 pH = 5 pH =
6 DI water pH = 12 5 min 3 2 0 0 0 0 0 0 45 min 5 3 1 0 0 0 0 0 125
min 5 4 3 0 0 0 0 0 Maximum color change = 5 No color change =
0
[0067] Based on the results shown in Table 2, pH 3 can be effective
to break down an ash aggolomerate. A pH of less than 3 is even more
effective.
EXAMPLE 3
[0068] A Corning Dura Trap.RTM. CO filter was loaded with ash and
then fired at 900.degree. C. for one hour. The fired filter was
air-cleaned using 100 psi air. Following air-cleaning, the filter
was placed into a container, and a nitric acid solution was poured
over the filter (approx. 1500 ml of solution) and soaked for a
predetermined period of time. The procedure was performed at pH=1
and pH=3, and using DI water, for varying time periods. After
soaking, the filter was water-rinsed. The results are shown in FIG.
5. The figure shows the impact of pH and time on ash removal.
Soaking at pH=1 for 5 minutes was sufficient to remove around 80%
of the ash that remained after air-cleaning. Additional soaking
time did not significantly increase ash removal.
EXAMPLE 4
[0069] A nitric acid solution (pH 1; approximately 2500 ml) was
poured over an air-cleaned filter (Corning Dura Trap.RTM. CO;
diameter 5.66''; length 6'') that had been previously ash coated
and fired at 900.degree. C. for one hour. Approximately 1000 ml of
the acid solution was absorbed onto the filter. After 5 minutes
soaking in the absorbed solution, the filter was rinsed. Ash
removal was calculated to be 72.7%.
EXAMPLE 5
[0070] The procedure of Example 4 was repeated, except that the
filter containing the absorbed solution was allowed to be soaked
for 25 minutes. Ash removal was calculated to be 84.4%.
EXAMPLE 6
[0071] Coated filters were evaluated using the method of Example 4.
The filters tested were Corning Dura Trap.RTM. CO and Corning Dura
Trap.RTM. RC filters. The filters were coated with a coating
containing a mixture of gamma-alumina and precious metals. The
results are shown in Table 3. A loss of coating material was
suspected as the cause of the CO filter efficiency results.
TABLE-US-00003 TABLE 3 Weight before Ash Actual After After Weight
Filter loading Tar- Loading loading cleaning Loss Efficiency Type
(g) get (g) (g) (g) (g) (%) CO 1193.11 5 g/l 13.06 1206.17 1193.6
12.57 96.3% RC 1776.4 25 g/l 45.65 1822.05 1792.12 29.93 65.6% RC
1852.2 25 g/l 44.76 1896.96 1857.04 39.92 89.2% CO 1217.8 25 g/l
39.57 1257.37 1216.99 40.38 102.1%
[0072] The principles and modes of operation of this invention have
been described above with reference to various exemplary and
preferred embodiments. As understood by those of skill in the art,
the overall invention, as defined by the claims, encompasses other
preferred embodiments not specifically enumerated herein.
* * * * *